Is it necessary for one afflicted by the evil eye to wash their entire body and hair when performing ghusl (ritual bathing) from the trace of the envier, taking into account that what is mentioned in the Sunnah is pouring from behind and that the amount of water used is small?

It is not necessary for the water to cover the entire body of the person afflicted by the evil eye when the 'ain (person who cast the evil eye) performs ghusl. Rather, it is sufficient to pour it over them. 'Amir washed his face, hands, elbows, knees, the ends of his feet, and the inside of his lower garment in a bowl, then poured the water over Sahl. It has also been reported that the water should be poured over the head of the afflicted person from behind, in a single pour.